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Vulnerabilities

Vulnerability · CVE-2026-42859

Neat VNC is a VNC server library.

Published May 11, 2026 · catalog updated Jun 17, 2026 · Neat VNC is a

Check if you run it

No confirmed exploitation is on record for CVE-2026-42859. EPSS is 0.76%. Act only if a listed version of Neat VNC is a is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Neat VNC is a).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.76%
Remediation
Advisory link
Affected products
See sources for product scope

Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security type 129 (RSA-AES-256) handshake with an oversized client RSA public key, causing rsa_aes_send_challenge in src/auth/rsa-aes.c to overflow a 1024-byte on-stack buffer when encrypting the server challenge. This results in at least a denial of service via server crash. This vulnerability is fixed in 0.9.6.

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-42859

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-42859. EPSS is 0.76%. Act only if a listed version of Neat VNC is a is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-120: Classic Buffer Overflow. EPSS 0.76%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. May 11, 2026 · NIST NVD

    Detected

    Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security type 129 (RSA-AES-256) handshake with an oversized client RSA public key, causing rsa_aes_send_challenge in src/auth/rsa

  2. Jun 17, 2026 · NIST NVD

    Updated

    Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security type 129 (RSA-AES-256) handshake with an oversized client RSA public key, causing rsa_aes_send_challenge in src/auth/rsa

Sources

  • CVE.orgVulnerability recordCVE-2026-42859

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-42859

    30-day exploitation probability 0.8%

    first.org
  • NIST NVDVulnerability recordCVE-2026-42859

    Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.